Field of the Invention
This invention relates generally to tires having multiple carcass plies that wrap around multiple bead cores on a single side of the tire, arid, more specifically, to a tire that has a bead core locking insert that eliminates a pullout step for one of the carcass plies or bands during fabrication. This step Includes wrapping one of the plies or bands completely around said multiple bead cores that are found on a single side of the tire. In certain embodiments, the tire is an aviation tire that has bands of multiple plies that are wrapped about multiple bead cores found on each side of the tire. The bead core, locking insert is found below the multiple, bead cores found on each side of the tire and is adjacent to the plies or bands, that wrap around the inside and outside bead cores, thereby locking these beads and associated plies or bands together.
Description of the Related Art
Those skilled in the art are familiar with tires having multiple beads and carcass piles that are wrapped around those multiple beads. These tires often have bias ply carcass constructions and are intended to carry very heavy loads although radial ply constructions are also known. Typical applications for such tires include mining, off road, earth moving, freight hauling, and aviation environments where the tires can be subjected to high stresses due to the high loads they must endure, whether these loads be transitory or shock loads versus steady state loads, or somewhere in. between, or combination thereof. For example, the loads experienced by aircraft tires can range from 1,200 to 78,800 pounds per tire.
Looking at FIG. 1, an example of an aircraft tire 100 having multiple carcass piles wrapped around multiple beads is shown that is currently on the market and that, is a H44.5×16.5-21 sized tire. The tire 100 defines circumferential X, axial Y and radial Z directions and has a tread portion 102, sidewall portions 104A, 104B and bead areas 106A, 106B which are used to secure the tire to a wheel or rim (not shown) when the tire is inflated according to means commonly known in the art, which causes the toe portion 110 of the bead area 106, which is located toward the interior of the tire near the inner liner 108, to press down on the wheel or rim seat (not shown), thereby supporting the sidewall 104 of the tire and preventing it from rotating. At the same time, the heel portion 112 of the bead area 106, which is found toward the exterior of the tire next to the sidewall 104, helps to limit the movement of the sidewall axially along the wheel or rim seat that typically has a flange (not shown) against which the heel 112 presses. The tread 102 has circumferential grooves 114 that help the tire maintain traction in wet conditions as these grooves allow for the displacement of water, thereby decreasing the likelihood of hydroplaning. More specifically, this tire has bias ply construction for its carcass plies which are grouped in bands 116 that are each wrapped around a different bead core 118. As shown, there are three bead cores 118 on each side of tire in the respective bead areas 106 that are each wrapped by a bead, core wrap 120, which is constructed in a manner commonly known in the art. Overall, the construction of the tire is essentially symmetrical about the equatorial plane E.
Turning, to FIG. 2, an enlarged front view of the left bead area 106A found on the tire 100 in FIG. 1 can be seen. Again, there are three bead cores 118 and associated bead core wraps 120 that are arranged side by side in the axial Y direction of the tire. The first or leftmost bead core USA has a first set or band 116A of carcass plies that extends from the summit or tread portion 102 of the tire 100 and that are wrapped around it and its wrap 120A, bead filler 119A and associated flipper (not shown for simplicity) in a clockwise fashion. The second or middle head core 118B has a second set or band 116B of carcass piles that extends from the summit or tread portion 102 of the tire 100 and that are wrapped around it, its bead filler 119B, its wrap 120B, and associated flipper (hot shown for simplicity) in a clockwise fashion while the third or rightmost bead core 118C also has a third set or band 116C of carcass plies that extends from the summit or tread portion 102 of the tire 100 and that are wrapped around it, its bead filler 119C, its wrap 120C, and associated flipper (not shown for simplicity) in a clockwise fashion. These same bands 116 extend from this bead 106A area through the summit or tread portion 102 of the tire 100 to another set of bead cores 118 found in the rightmost head area 106B and are wrapped around them in a counterclockwise fashion (best seen in FIGS. 1 and 3).
In this tire, the first, band 116A comprises two individual carcass layers or plies while the second band 116B and third band 116C each comprise four individual carcass layers or plies. The cords of the plies are made from nylon and are embedded in an elastomeric mix and are angled from 40 to 72 degrees from the circumferential X direction or equatorial plane E of the tire 100, with the angle going from positive to negative from one ply to the other ply, Other configurations and materials are also used. For example, the cords can be made from nylon, rayon, cotton or any other suitable material
It should be noted that there are examples of such tires where the wrapping of the bands of plies are in the opposite direction just described and/or where more than one band is wrapped around the same bead core. Also, as is the ease here, there may be a fourth band 122 that extends from the summit or tread portion, along the outside or exterior portion of the sidewall 104A nearest the exterior of the tire and continues underneath all the cores 118A, 118B, 118C and bands 116 that have been wrapped around them. This is called the turn down band 122 and in this ease it comprises two separate carcass layers with cords made from nylon that are embedded in an elastomeric mix and are angled from 40 to 72 degrees from the circumferential direction X or equatorial plane E of the tire in like fashion to the other plies that have been already described. Other configurations and materials are known,
Finally, a fifth band 124 is utilized that extends from the summit or tread portion, along, the interior portion of the sidewall 104A of the tire adjacent the inner liner 108 and extends underneath all four of the previous bands 116, 122 and underneath all the bead cores 118A, 118B, 118C. The Fifth and fourth bands 124, 122 overlap over the entire distance in the axial Y direction found beneath the cores 118A, 118B, 119C so that once the tire is cured and the plies have all cured together and adhered to each other, these cores are effectively locked to together, allowing the plies to perform their function and create an effective spine for the tire to transmit the heavy loads exerted on it from the summit of the tire through the carcass piles to the bead cores and from there to the wheel or rim as is necessary. For this tire, the fifth band 124 comprises two separate carcass layers with cords made from nylon that are embedded in an elastomeric mix and are angled from 40 to 72 degrees from the circumferential X direction or equatorial plane E of the tire in like mariner as described above for the other plies. Other configurations and materials are known.
Beneath and to the sides of the fourth and fifth bands 122, 124, one can see first and second chafer strips 126A, 128A (sometimes referred to as finishing strips) that are found in the bead area 106 that partially surround the multi-bead assembly and therefor separate the bands found within this assembly from the wheel or vim during use and are intended to protect the same from damage that can happen should movement occur between the bead portions and the wheel. These components are routinely found in tires of all sorts including those using only a single bead core per bead area. In addition, these strips may have butyl or some other chemical property similar to the inner liner In them that helps to retain air so that the tire is less prone to deflation over time. The chafer strips are typically square woven, monofilament, calendered fabric and are not intended to provide any structural benefit to the tire. As a result, they do not lock the bead cores together. Although there can be a single chafer strip, most tires including tins one have two chaffer strips in each bead area found on each side of the tire as shown by FIGS. 2 and 3.
Focusing, now on FIG. 3, a schematic view of the construction of the right bead area 106B of FIG. 1 is shown for enhanced clarity. The fourth or rightmost bead core 118D has the first set or band 116A of carcass plies that extends from the summit or tread portion of the tire and that are wrapped around it in a counterclockwise fashion. The fifth or middle bead core USE has the second set or band 116B of carcass plies that extends from the summit or tread portion of the tire and that are wrapped around it in a counterclockwise fashion while the sixth or leftmost bead core USE also has a third set or band 116C of carcass plies that extends from the summit or tread portion of the tire and that are wrapped around it In a counterclockwise fashion. Note other components such as bead fillers and flippers are also present but not shown for simplicity.
Put into other words, the bead cores have carcass plies, which extend from one bead portion to the other bead portion through the sidewalls and summit or tread portion of the tire, wrapped around each of them in the following manner in both bead portions. The carcasses plies approach the bead core from the interior side of the tire, which is the side of the tire that is nearest the inner liner, and extend generally radially Z downward. They then continue underneath the bead cores in the axial Y direction and exit along the exterior surface of the bead cores, so called since this surface faces toward the exterior of the tire. From there, they extend in a general upward radial Z direction. This is typically done symmetrically about the equatorial plane E of the tire so the wrapping is consistent on both sides of the tire. However, there are examples where the wrapping is done in the opposite direction or in both directions.
The fourth band or turn down band 122 extends from the summit or tread portion, along the outside portion of the side wail that is nearest, the exterior of the tire and continues underneath all the cores 118D, 118E, 118F and bands 116 that have been wrapped around them. The fifth band 124 extends from the summit along the interior portion of the sidewall of the tire adjacent the inner liner and extends underneath all four of the previous bands 116 and underneath all the bead cores 118D, 118E, 118F in this bead area 106B. The fifth and fourth bands 122, 124 overlap over the entire distance in the axial Y direction found beneath the cores so that once the tire is cured and the bands have all cured together and adhered to each other, these cores 118D, 118E, 118F are effectively locked to together as previously described. Beneath and to the sides of the fourth and fifth bands, one can see third and fourth chafer strips 126B, 128B that are found In the bead area that partially surround the multi-bead assembly and therefor separate the bands found within this assembly from the wheel or rim during use as described above for the first bead area.
As is often the case with tires, the fourth though six bead cores 118D, 118E, 118F and third and fourth chaffer strips 126B, 128B found in the second bead area 106B have the same material properties and construction and are configured symmetrically about the equatorial plane E as compared to their counterparts found in the first bead area 106A. Specifically, the first bead core 118A matches up with the fourth bead core 118D, the second bead core 118B matches up with the fifth bead core 118E, the third bead core 118C matches up with the sixth bead core 118F, the first chaffer strip 126A matches up with the third chaffer strip 126B and the second chaffer strip 128A matches up with the fourth chaffer strip 128B, etc. The places where these tire components terminate are also in approximately the equivalent place from one side of the tire to the other, maintaining the symmetry of the tire about the equatorial plane E. The terminations for the plies that wrap around the bead cores is usually a suitable distance above the topmost extent of the bead filler, allowing the turned up portion of one of the plies to adhere to its main portion found on the other side of the bead core and bead filler. In some cases, asymmetrical designs are employed.
However, in order to show manufacturing and/or design variability, it should be noted that the schematic of FIG. 3 shows the pullout band 124 extending up radially Z past the third bead core 118D while it does not do this in FIG. 1, This can represent a design choice or manufacturing tolerances as plies often move during the manufacturing process, which is described in more detail below, such that the position a ply is originally laid may not be its final position. For example, a ply may be originally laid with the upward extension past the third bead core shown in FIG. 3 but may move during the molding and/or laying down steps of the manufacturing process, resulting in the position shown in FIG. 2 where this extension that terminates radially upward past the third bead core does not exist.
The methods of manufacturing tires with multiple bead cores are well known in the art and these processes and the equipment used in these processes are described by U.S. Pat. Nos. 4,445,962; 2,926,721 and 2,951,526, During the manufacturing process of these tires, a liner is first wrapped about the building drum then successive separate plies are then wrapped about the drum, the bead core is then positioned appropriately on the drum, finally a turn up of the plies about the bead core is then effected. Additional plies are wrapped about the drum and a second bead core is placed against the first set of plies and first bead core, after which a turn up of the additional plies is accomplished. This process can be repeated as necessary depending on how many sets of bead cores and associated wrapped plies are desired. Then the sidewalls shoulder rubber, finishing strips and tread can be added.
Once the green tire has been created, the tire drum is collapsed and the green tire is then placed into a molding apparatus that changes the configuration of the green tire front a flat cylindrical band to a toroidal shape. It is in this vulcanizing process that the beads cores, plies and rubber material physically are moved in configuration to the toroidal form such as shown by FIG. 1. Also, it is at this point that the various bands of carcass layers or plies adhere to each other, locking the bead cores together thereby creating a reinforced structure able to carry heavier loads than tires that have only a single bead core in each bead area on each side of the tire.
During the manufacturing process of the tire already described, the first band laid down sequentially on the building drum is the structural fifth band 124 mentioned above that eventually is used to help lock all the bead cores together. Initially, the outer portions of this band are wrapped underneath the building drum so that the other bead cores and plies can be applied on top of it without haying the extra length at either end of this band interfering with the laying of the other components. It is therefore necessary later to manually pullout this band on the tire building drum once all the bead cores and associated piles have been laid and turned up so that it can be wrapped around ail of the bead cores and satisfy its locking function.
FIG. 4 illustrates this pullout and wrap around step necessary during this manufacturing process. As can be imagined due to the sticky nature of the carcass plies, such a manual pullout requires an extreme amount of physical effort and repetitive motion as this step is performed repeatedly around the circumference of the building drum 132 which is periodically indexed so this fifth band 124 can be positioned correctly about the entire circumference of the green tire intermediate 130. The operators are required to bend over to reach within the building drum while doing this, which can cause them to have poor posture and the amount of pinch force necessary to accomplish this can be as high as 80 lbs of pinch force. Hence, this tire design and associated building process pose ergonomic challenges during the tire building process as well as inefficiency that increase the time necessary to make such a tire, which raises the cost of the tire.
For many aircraft tire applications, a pullout ply and a turn down ply are required in order to lock the multiple bead cores and associated wrapped around plies together. Both are required for some tires that are subjected to very high loads, such as when an aircraft is taking off or landing for instance, that a tire not having the turn down band will fail. As a result, this construction has been considered necessary for many commercial and military aircraft applications while the problems it presents have not been solved for several decades. In less demanding applications, the pull out band has not been necessary.
When developing a tire for some of these demanding aviation applications, it is typical to use a double overload test to determine if a tire can withstand approximately twice its rated load should one tire of a pair of tires located on the landing gear fail. That is to say, the surviving tire must carry the load safely until the plane can stop. Many tires intended for these harsh conditions must pass this test. This test, can be performed using equipment known in the art. For commercial aircraft manufacturers who required such testing, this can involve a single test -cycle where the tire is subjected to a rationalized Load Speed Time curve at 1.87 times the rated load. To date, no design variations that lack the pullout of the innermost ply and that have been subjected to this test and have passed,
Accordingly, it is desirable to find a construction for a tire that has multiple bead cores and multiple carcass plies wrapped around the multiple bead cores that also has a way to lock said beads together in a cost efficient manner that does not require manual manipulation of a carcass ply and in a sufficiently durable manner so that it can support the heavy loads that the tire is required to handle in the field. For tires in the aviation sector, it is desirable if the new construction can pass the dynamometer double overload test reliably and consistently when required.